A
BC
Fig. A: This annoying device eludes detection.
Fig. B: Several small, high-frequency speakers; the
rating isn’t important.
Fig. C: Installing the parts into an innocuous wall
wart case makes it hard to find the source of the
annoying beep!
long for the unsuspecting victim to find it! If you
plan to use a wall wart cabinet for the device like we
did, ensure that there’s no connection between the
plug prongs and the AC lines. It’s a good idea to
remove the prongs completely.
Photography by Brad Graham
Some other good hiding places might be a pop
can, lunch box, wall clock, tissue box, or even a
working appliance. A solid cabinet will need a small
hole for the speaker. We found that a ¼" hole was
large enough for the tiny 2" speaker we used. You
can also use a piezo buzzer instead of a speaker,
which would make the unit even smaller and possibly louder owing to the very good high-pitched
operation of the piezo element. To use a piezo buzzer
in place of the speaker, connect resistor R4 (which
used to connect to one of the speaker terminals)
directly to the +9V line, where the other speaker
terminal used to connect.
Now you can place the piezo buzzer in parallel
with R4 to make it function. This is done because
the piezo element will offer very high resistance as
compared to the very low resistance of the speaker,
and the current from the battery needs to flow to
transistor Q2’s collector.
The final product looks at home just about
anywhere there is a wall socket, and can be easily
hidden under furniture or inside another appliance
for truly covert, mind-warping, annoying fun and
games. We covered up the voltage switch from the
original wall wart with black tape, and the little hole
on the top of the case is barely large enough to pass
a decent amount of high-pitched sound.
With the component values given, the beep emits
about once every 3 minutes and lasts for approximately 5 seconds, just enough time to entice the
victim to look for the source of the sound before it
goes silent. We like to drop the unit in a room, then
claim that we can’t hear any beeping. This really gets
the “beeper hunter” ticked off, and they try even
harder to track down the evasive beeping thing to
no avail. “I don’t hear anything, pal, maybe you need
an ear exam, or you should stop listening to pirated
music on your MP3 player. I heard that the new copy
protection can make your ears ring for days!”
Reprinted with permission from 51 High-Tech
Practical Jokes for the Evil Genius (McGraw-Hill/TAB
Electronics), by Brad Graham and Kathy McGowan.
Brad Graham is an author and inventor of electronics,
custom bikes, robots, and Evil Genius works. He also hosts
atomiczombie.com with his partner Kathy McGowan.
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